The Chinese word for to stretch is
拉伸

lā shēn

Chinese Definition

stretch
1. 伸展；拉长；延伸；夸大
Components
拉
(Alternative form 摺, 搚, 拹)
1. to pull; to drag; to tug
將窗簾拉laai1 落嚟 - pull down window blinds
2. to transport by vehicle; to haul; to carry on a vehicle
3. to play (a bowed instrument, an accordion, etc.)
拉二胡 - to play the erhu
我不會拉小提琴。 - I don't know how to play the violin.
4. to drag out; to draw out
5. (Mainland) to owe; to be in arrears
6. to lead (a group to a place); to move (a group to a place)
7. to help; to lend (a hand)
8. to invite; to recruit
9. to drag in; to implicate
10. to draw in; to canvass; to solicit; to attract
11. to organize (a group); to form (a group)
12. (Cantonese) to arrest
13. (dialectal) to bring up; to raise
14. (Mainland, colloquial) to chat
拉家常 - to chitchat
15. to excrete
拉大便 - to poo
16. (Hong Kong, internet slang) to cause a thread to sink to the bottom of list of threads; to "pull".
(syn, yue, pull)
(ant, yue, 推, push)
17. (dated Shanghainese Wu) (Used to mark the perfective aspect.)
Synonyms: 拉哉, 拉哩
勿吃要罰個！吃拉哉。 - tr=, If you didn't eat you would be punished! Finish the food (ie. have the food be finished)., SH, ref=2010, Qian Nairong, 《從〈滬語便商〉所見的老上海話時態》 (Tenses and Aspects? Old Shanghai
18. (Mainland) to cut; to slit; to slash
(Alternative form 剌)
19. (Mainland, colloquial) section; part
20. Alternative form of 落 (là)
21. Used in 拉拉蛄 (,) Alternative form of 蝲蝲蛄
22. (A verbal suffix.)
伸
1. to extend; to stretch out
伸長兩隻手 - to extend two hands
2. to report
3. (Hakka, Hokkien) to be left; to remain
(Alternative form 剩, 賰, 偆)

Translations for 伸 and their definitions

伸展
1. v. to stretch; to expand; to spread
2. adj. (Sichuan) comfortable
3. adj. (Sichuan) flat; smoothed out
4. adj. (Sichuan) clear; distinct
5. adj. (Sichuan, Dafang) pretty; neat
6. adj. (Sichuan) smooth; unhindered
7. adj. (Dafang) wealthy
8. adj. (Dafang) straight
9. adj. (Dafang) eloquent

拉
(Alternative form 摺, 搚, 拹)
1. to pull; to drag; to tug
將窗簾拉laai1 落嚟 - pull down window blinds
2. to transport by vehicle; to haul; to carry on a vehicle
3. to play (a bowed instrument, an accordion, etc.)
拉二胡 - to play the erhu
我不會拉小提琴。 - I don't know how to play the violin.
4. to drag out; to draw out
5. (Mainland) to owe; to be in arrears
6. to lead (a group to a place); to move (a group to a place)
7. to help; to lend (a hand)
8. to invite; to recruit
9. to drag in; to implicate
10. to draw in; to canvass; to solicit; to attract
11. to organize (a group); to form (a group)
12. (Cantonese) to arrest
13. (dialectal) to bring up; to raise
14. (Mainland, colloquial) to chat
拉家常 - to chitchat
15. to excrete
拉大便 - to poo
16. (Hong Kong, internet slang) to cause a thread to sink to the bottom of list of threads; to "pull".
(syn, yue, pull)
(ant, yue, 推, push)
17. (dated Shanghainese Wu) (Used to mark the perfective aspect.)
Synonyms: 拉哉, 拉哩
勿吃要罰個！吃拉哉。 - tr=, If you didn't eat you would be punished! Finish the food (ie. have the food be finished)., SH, ref=2010, Qian Nairong, 《從〈滬語便商〉所見的老上海話時態》 (Tenses and Aspects? Old Shanghai
18. (Mainland) to cut; to slit; to slash
(Alternative form 剌)
19. (Mainland, colloquial) section; part
20. Alternative form of 落 (là)
21. Used in 拉拉蛄 (,) Alternative form of 蝲蝲蛄
22. (A verbal suffix.)

拉長
1. v. to lengthen by pulling; to stretch; to elongate
2. v. to prolong; to extend
把時段拉長一點 - to extend a period of time
3. v. to add; to expand